Hey Samuel – welcome to Bugzilla! :) For first bugs, we wait until there's a patch submitted before assigning the bug. As such you'll need to set up your build environment, create a patch, and submit it. If you need help at all during this process, feel free to ask questions in this bug or on irc.

Comment on attachment 8696258[details][diff][review]
bug_1228037_remove_geckoPreferences.patch
Review of attachment 8696258[details][diff][review]:
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Hey Samuel. The patch looks good to me but it doesn't apply on the latest fx-team so I can't push it to our try test servers. Do you mind rebasing your patch? Our source files have moved so that's likely the issue. You can find them at mobile/android/base/java/...

Once the patch is rebased, we can send it to our test servers and once the push goes green, we can land it.
Also, I apologize for the delay – the team is at a conference this week so I've been intermittently available. I'll do my best to get to future patches more quickly.

Our test suites often get intermittent failures and this looks like one of them. Our harness will automatically rerun failures (as you can see from the green push). Additionally, if you click a failing test suite, you can look at the bar on the bottom of the screen and see if it matches any existing known intermittent failures, which are also listed on that bar (your failure does match).
This looks good to me and is ready for check-in!